Hello,
I work here at 123-reg.
123-reg is now a direct registrar, accredited with all key registries. We are now moving our entire portfolio of domain names we hold for our customers into our control rather than using third parties. This will give our customers a better domain name management experience and allow us to offer a better support experience. To do this we need to transition domain names which does take about 5 days to complete. We are using the domain name renewal as a trigger for this.
When we auto renew domain names we are doing this 7 days prior to the expiration date to ensure that the transition can complete before the expiration date and avoid any down time. We will attempt to auto renew every domain name, however at times this does not happen. As with all internet based systems errors can occur, or we may not have been able to collect payment or any other reason. I cannot say why your domain name did not automatically renew from the details here.
The majority of customers will not see any effect caused by the transition and I do apologise for any inconvenience you have been caused by the transition.
If you wish to find out more about this transition please see the below guide:
http://www.123-reg.co.uk/support/answers/Domains/Domains-Explained/understanding-the-domain-transition-period-4263/
Regards,
Nerys